Sub-soil drainage piping

ABSTRACT

A sub-soil drainage pipe segment 12 comprises a first round cylindrical portion 14 forming a socket 16 and a second round cylindrical portion 18 integral with and extending from the first portion, the inside diameter of the first portion being substantially equal to the outside diameter of the second portion. In the second portion there are a plurality of circumferentially spaced, longitudinally extending slots 22. The slots are defined by longitudinally extending side walls which diverge from the outside inwardly. A plain end 20 of the second portion forms a spigot which is receivable in the socket of a similar segment, so that a number of such segments can be interconnected end-to-end to form a sub-soil drainage line.

FIELD OF THE INVENTION

This invention relates to sub-soil drainage piping. More particularly,it relates to a sub-soil drainage pipe segment, and to a sub-soildrainage line made up of a number of such segments.

BACKGROUND TO THE INVENTION

Clay pipe segments, pitch-fibre pipes, and extruded plastics pipes havefor many years been used in sub-soil drainage systems. In the systemsmaking use of clay pipe segments, water-perviousness is provided by theporosity of the clay and by imperfect fitting of adjacent pipe segments.Although durable, clay pipes are expensive. In the pitch-fibre systemsthe pipes are drilled to render them water-pervious. In extrudedplastics systems, the pipes are provided with transverse saw cuts torender them water-pervious. In both the pitch-fibre and extrudedplastics systems, it is not possible readily to provide sufficientlynarrow drill holes or saw cuts and this usually makes it necessary toprovide a porous filler such as ash or gravel around the pipes duringlaying. This increases the labour cost. Furthermore, the drill holes andsaw cuts are inevitably rough and of uniform width throughout thethickness of the pipe, leading to sand and other particles becominglodged in the openings and clogging them up.

It is an object of the present invention to provide a relativelyinexpensive sub-soil drainage pipe segment which will not suffer fromthe disadvantages set out above.

SUMMARY OF THE INVENTION

According to the invention there is provided a sub-soil drainage pipesegment which has connecting formations at opposite ends thereof,whereby a number of such segments can be interconnected end-to-end toform a sub-soil drainage line, the segment further having a plurality ofcircumferentially spaced, longitudinally extending slots therein whichrender the segment water-pervious.

The connecting formations may be complementary spigot and socketformations, whereby the spigot formation of one such pipe segment isreceivable in a socket formed by the socket formation of another suchpipe segment.

Each slot may, across its entire width and depth, be open longitudinallyin the direction of the socket.

The pipe segment may comprise a first round cylindrical portionextending to one end of the pipe segment and forming the socket, and asecond round cylindrical portion integral with and extending from thefirst cylindrical portion to the other end of the segment, the insidediameter of the first cylindrical portion being equal to or slightlygreater than the outside diameter of the second cylindrical portion.

The length of the pipe segment is preferably less than twice the outsidediameter of the second cylindrical portion.

Each slot may be defined by a pair of longitudinally extending wallswhich diverge from the outside of the segment inwardly.

The invention extends to a sub-soil drainage pipe segment which has aplurality of circumferentially spaced, longitudinally extending slotstherein, each slot being defined by a pair of longitudinally extendingwalls which diverge from the outside of the segment inwardly.

The invention further extends to a sub-soil drainage line comprising aplurality of segments as defined above, connected together end-to-end.

The invention will now be described in more detail, by way of example,with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a side view of a number of sub-soil draininge pipe segments inaccordance with the invention, the segments having been assembled toform a sub-soil drainage line;

FIG. 2 is an end view (from the direction II in FIG. 3) of one of thepipe-segments;

FIG. 3 is an enlargement of part of FIG. 3 (the part indicated at III);and

FIG. 4 is a longitudinal section of the pipe segment, taken on lineIV--IV in FIG. 2.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Referring first to FIG. 1, reference numeral 10 generally indicates partof a sub-soil drainage line which is made up of a number of sub-soilpipe segments 12 assembled together in end-to-end fashion. The pipesegments are injection moulded from a suitable plastics material.

Referring now to FIGS. 2 to 4, each pipe segment 12 comprises a firstround cylindrical portion 14 which extends to one end of the pipesegment and defines a socket 16, and a second round cylindrical portion18 integral with and extending from the first portion to the other endof the pipe segment. A plain end 20 of the portion 18 forms a spigotwhich is receivable in the socket 16 of a similar pipe segment, thusenabling a plurality of such pipe segments to be interconnectedend-to-end as illustrated in FIG. 1. The outside diameter of the portion18 is substantially equal to the inside diameter of the socket 16 sothat the pipe segments are a tight fit, one into the other. In theportion 18 there are a plurality of circumferentially spaced,longitudinally extending slots 22 which render the pipe segmentwater-pervious.

Each slot 22 is defined by a pair of longitudinally extending side walls24 which deverge from the outside of the pipe segment inwardly. Width wof the slots 22 at the outside of the portion 18 is in the order of 0.6mm, and width at the inside in the order of 1.5 mm. The depth D of theslots 22 (i.e. the wall thickness of the portion 18) is in the order of1.5 mm. The outside diameter of the portion 18 is in the order of 70 to80 mm and the length of the segments is roughtly 30% greater than theoutside diameter of the portion 18. It will be appreciated that thesedimensions are given purely by way of example and are in no way intendedto limit the scope of the invention.

Each slot 22, across its entire depth and width, is open longitudinallyin the direction of the socket 16. This enables the pipe segment 12 tobe produced in a single injection moulding cycle without the need forcollapsible cores. Thus, a mould for producing the pipe segment 12 mayhave an outer part and a core. The outer part of the mould will have afirst portion of small diameter corresponding to the outside diameter ofthe portion 18, and a second portion of large diameter corresponding tothe outside diameter of the portion 14. The core will have a firstportion of small diameter corresponding to the inside diameter of theportion 18, a second portion of large diameter corresponding to thediameter of the socket 16, and a number of circumferentially spacedridges protruding radially outwardly from the first portion of the coreand extending longitudinally from the second portion of the core, eachridge corresponding to a respective one of the slots 22. When the twoparts of the mould are closed, the ridges will touch the first portionof the outer part of the mould. It will be clear that in theconstruction illustrated, it will be possible to remove a moulded pipesegment 12 longitudinally from the core without the core having to becollapsible.

By producing the pipe segments by injection moulding in this manner, theslots 22 can be provided with very smooth side walls 24. This, inaddition to the inwardly diverging construction of the slots willminimise the tendency to clog. It is also possible, in this manner, toprovide slots having a width w which is substantailly less than thatwhich can conveniently be produced by drilling or sawing.

If desired, the mould be of the multiple core type so that two or morepipe segments 12 can be produced simultaneously in a single mouldingcycle. In this event the mould may be such that two or more pipesegments of progressively decreasing diameter can be producedsimultaneously, the diameters being chosen such that the pipe segmentsproduced during each injection moulding cycle can be nested one in theother. This will substantially reduce space requirements for packagingand transportation purposes. In assembling a drainage line from suchsegments of differing diameter, a first part may be assembled from anumber of pipe segments of the smallest diameter, followed by a secondpart assembled from a number of pipe segments of the next greaterdiameter, and so on. The fact that two adjacent pipe segments ofdiffering diameter will have a certain amount of clearance between themwill not matter as water seepage is desired rather than to be avoided.

Although the pipe segments 12 can be fitted together manually, they lendthemselves particularly to mechanised fitting together and laying. Thismay, for example, be achieved by providing a trench-digging machine witha guide tube through which the pipe segments can be guided into thetrench immediately after it has been dug by the trench-digging machine.At the mouth of the tube there may be a loading bay into which pipesegments can be loaded, and a reciprocating mechanism, which may operatemechanicaly or hydraulically, for pressing each pipe segment intoengagement with the pipe segment that precedes it.

If desired, adjacent pipe segments may be secured together adhesively,e.g. by means of applying a small amount of suitable solvent to theinterengaging spigot and socket formations.

We claim:
 1. A sub-soil drainage pipe segment which has connectingformations at opposite ends thereof, whereby a number of such segmentscan be interconnected end-to-end to form a sub-soil drainage line, thesegment further having a plurality of circumferentially spaced,longitudinally extending slots therein which render the segmentwater-pervious, wherein the connecting formations are complementaryspigot and socket formations, whereby the spigot formation of one suchpipe segment is receivable in a socket formed by the socket formation ofanother such pipe segment, wherein each slot, across its entire widthand depth, opens into the socket at one end of the slot and wherein thepipe segment comprises a first round cylindrical portion extending toone end of the pipe segment and forming the socket, and a second roundcylindrical portion integral with and extending from the firstcylindrical portion to the other end of the segment, the inside diameterof the first cylindrical portion being equal to or slightly greater thatthe outside diameter of the second cylindrical portion.
 2. A sub-soildrainage pipe segment as claimed in claim 1, wherein the length of thepipe segment is less than twice the outside diameter of the secondcylindrical portion.
 3. A sub-soil drainage pipe segment according toclaim 1, wherein each slot is defined by a pair of longitudinallyextending walls which diverge from the outside of the segment inwardly.